From: Nathan Moinvaziri <nathan@nathanm.com>
Date: Thu, 22 Jan 2026 01:10:14 +0000 (-0800)
Subject: Move DoNotOptimize in benchmark loop to prevent it being optimized away
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=49dbc2f56e380d4fb670efc858919445d13071ab;p=thirdparty%2Fzlib-ng.git

Move DoNotOptimize in benchmark loop to prevent it being optimized away

In some cases I've noticed incorrect 0 benchmark results from compiler
optimizing away len during hash benchmarks.
---

diff --git a/test/benchmarks/benchmark_adler32.cc b/test/benchmarks/benchmark_adler32.cc
index 8fb213004..5ee9102e2 100644
--- a/test/benchmarks/benchmark_adler32.cc
+++ b/test/benchmarks/benchmark_adler32.cc
@@ -41,10 +41,10 @@ public:
                 misalign = 0;
             else
                 misalign += (DO_ALIGNED) ? 16 : 1;
-        }
 
-        // Prevent the result from being optimized away
-        benchmark::DoNotOptimize(hash);
+            // Prevent the result from being optimized away
+            benchmark::DoNotOptimize(hash);
+        }
     }
 
     void TearDown(const ::benchmark::State&) {
diff --git a/test/benchmarks/benchmark_adler32_copy.cc b/test/benchmarks/benchmark_adler32_copy.cc
index 9d2994f4a..6d913b1d1 100644
--- a/test/benchmarks/benchmark_adler32_copy.cc
+++ b/test/benchmarks/benchmark_adler32_copy.cc
@@ -45,10 +45,10 @@ public:
                 misalign = 0;
             else
                 misalign += (DO_ALIGNED) ? 16 : 1;
-        }
 
-        // Prevent the result from being optimized away
-        benchmark::DoNotOptimize(hash);
+            // Prevent the result from being optimized away
+            benchmark::DoNotOptimize(hash);
+        }
     }
 
     void TearDown(const ::benchmark::State&) {
diff --git a/test/benchmarks/benchmark_compare256.cc b/test/benchmarks/benchmark_compare256.cc
index 4b616f5a5..eb103af0d 100644
--- a/test/benchmarks/benchmark_compare256.cc
+++ b/test/benchmarks/benchmark_compare256.cc
@@ -49,10 +49,10 @@ public:
                 misalign = 0;
             else
                 misalign++;
-        }
 
-        // Prevent the result from being optimized away
-        benchmark::DoNotOptimize(len);
+            // Prevent the result from being optimized away
+            benchmark::DoNotOptimize(len);
+        }
     }
 
     void TearDown(const ::benchmark::State&) {
diff --git a/test/benchmarks/benchmark_compare256_rle.cc b/test/benchmarks/benchmark_compare256_rle.cc
index 7e6551dbd..96489cf59 100644
--- a/test/benchmarks/benchmark_compare256_rle.cc
+++ b/test/benchmarks/benchmark_compare256_rle.cc
@@ -47,10 +47,10 @@ public:
                 misalign = 0;
             else
                 misalign++;
-        }
 
-        // Prevent the result from being optimized away
-        benchmark::DoNotOptimize(len);
+            // Prevent the result from being optimized away
+            benchmark::DoNotOptimize(len);
+        }
     }
 
     void TearDown(const ::benchmark::State&) {
diff --git a/test/benchmarks/benchmark_compress.cc b/test/benchmarks/benchmark_compress.cc
index b1a082da8..ebaf76cc4 100644
--- a/test/benchmarks/benchmark_compress.cc
+++ b/test/benchmarks/benchmark_compress.cc
@@ -54,9 +54,10 @@ public:
                 fprintf(stderr, "compress() failed with error %d\n", err);
                 abort();
             }
-        }
 
-        benchmark::DoNotOptimize(err);
+            // Prevent the result from being optimized away
+            benchmark::DoNotOptimize(err);
+        }
     }
 
     void TearDown(const ::benchmark::State&) {
diff --git a/test/benchmarks/benchmark_crc32.cc b/test/benchmarks/benchmark_crc32.cc
index df7eaec3e..b30b1855f 100644
--- a/test/benchmarks/benchmark_crc32.cc
+++ b/test/benchmarks/benchmark_crc32.cc
@@ -41,10 +41,10 @@ public:
                 misalign = 0;
             else
                 misalign += (DO_ALIGNED) ? 16 : 1;
-        }
 
-        // Prevent the result from being optimized away
-        benchmark::DoNotOptimize(hash);
+            // Prevent the result from being optimized away
+            benchmark::DoNotOptimize(hash);
+        }
     }
 
     void TearDown(const ::benchmark::State&) {
diff --git a/test/benchmarks/benchmark_crc32_copy.cc b/test/benchmarks/benchmark_crc32_copy.cc
index aa5c3f9e2..2d054dba4 100644
--- a/test/benchmarks/benchmark_crc32_copy.cc
+++ b/test/benchmarks/benchmark_crc32_copy.cc
@@ -45,10 +45,10 @@ public:
                 misalign = 0;
             else
                 misalign += (DO_ALIGNED) ? 16 : 1;
-        }
 
-        // Prevent the result from being optimized away
-        benchmark::DoNotOptimize(hash);
+            // Prevent the result from being optimized away
+            benchmark::DoNotOptimize(hash);
+        }
     }
 
     void TearDown(const ::benchmark::State&) {